<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <script src="./lib/vue.js" type="text/javascript" charset="utf-8"></script>
        <title>Document</title>
    </head>
    <body>
        <div id="app">
            <input type="text" v-model="username" value="">
            <!-- v-model 等同于  @input="username = $event.target.value" :value="username" 做了这些操作-->
            <input type="text" @input="username = $event.target.value" :value="username">
            <h3>{{ username }}</h3>
        </div>
    </body>
    <script>
        let app = new Vue({
            el:"#app",
            data:{
                username:'123'
            }
        })
    </script>
</html>